Suspended railway having a magnetic suspended guide of its vehicles

ABSTRACT

A suspended railway system utilizing a magnetic guide for vehicles and at least a support beam which is partly enclosed by the vehicle as a support member along the path of travel. The suspended railway system has, in the area of a switch, at least three support beams which are tapered on one side toward the central portion of the switch and terminate at the central portion. A first support beam extends from the switch entrance into the central portion of the switch and is arranged between the remaining two support beams. The remaining two support beams extend from the central portion of the switch to the switch exit. The switching function from one path of travel to another path of travel is accomplished by electromagnetic principles.

[ Nov. 12, 1974 1 1 SUSPENDED RAILWAY HAVING A MAGNETIC SUSPENDED GUIDE OF ITS VEHICLES [75] lnventor: Ulf Steenbeck, Miesbach, Germany [73] Assignee: Messerschmitt-Bolkow-Blohm Ga i, Muai fi y [22] Filed: Dec. 29, 1972 [21] Appl. No.: 319,908

[30] Foreign Application Priority Data Jan. 15, 1972 Germany 2201820 [52] US. Cl. 104/130, 104/105, 104/148 MS [51] Int. Cl EOlb 25/06 [58] Field of Search 104/130, 105, 46, 148 LM, 104/148 MS, 148 SS [56] References Cited UNlTED STATES PATENTS 3,451,351 6/1969 Hawes 104/130 3,628,462 12/1971 Holt Primary Examiner-M. Henson Wood, .Ir.

Assistant ExaminerD. W. Keen Attorney, Agent, or Firm-Woodhams, Blanchard and Flynn [57] ABSTRACT A suspended railway system utilizing a magnetic guide for vehicles and at least a support beam which is partly enclosed by the vehicle as a support member along the path of travel. The suspended railway system has, in the area of a switch, at least three support beams which are tapered on one side toward the central portion of the switch and terminate at the central portion. A first support beam extends from the switch entrance into the central portion of the switch and is arranged between the remaining two support beams. The remaining two support beams extend from the central portion of the switch to the switch exit. The switching function from one path of travel to another path of travel is accomplished by electromagnetic principles.

3,712,239 1/1973 Colovas 104/130 7 FOREIGN PATENTS OR APPLICATIONS 11 Claims, 7 Drawing Figures 707,032 6/1941 Germany 104/148 MS 14 22 I9 8 m tr 24 r a 211 if I mum I F t \T" 1 \l \\I --%\\\-\i1l 17 PNENTEB NOV 12 974 SHEET 2 of 3 Fig.2

SUSPENDED RAILWAY HAVING A MAGNETIC SUSPENDED GUIDE OF ITS VEHICLES For supporting and guiding vehicles of rail-mounted tracks, it is known to utilize the attractive forces between electromagnets and magnetically conductive rails and to control same in such a manner that the vehicles are held in a freely suspended condition and are guided freely suspended with respect to these rails. In such a known railway (German Pat. No. 707 032) for example, vehicles are held in a suspended position by electromagnets (support magnets) which act attractively on driving rails extending above or below said vehicles and additionally are guided by electromagnets (guide magnets) arranged on both sides in lateral direction with respect to side of the rails. This lateral guide has the advantage that in the Zone of switches, no adjustable switch parts are needed. To steer toward a desired direction of travel, it may only be necessary to render all guide magnets of one vehicle side inoperative. If, for example, in a switch only the electromagnets of the right vehicle side are in operation, then all vehicles automatically steer toward the right.

The arrangement of the electromagnets and rails chosen in the known suspended guide is, however, useable only for a so-called inside enclosure of the vehicles, that is, the rails which cooperate with the electromagnets as an armature are arranged with the associated supports or support beams outside of the vehicle profile. This causes a considerably greater gauge for the path of travel than in a suspended railway having a magnetic suspended guide of the vehicles and a central support beam partially enclosed by said vehicles which functions as a support construction for the path of travel (Transrapid of the Krauss-Maffei AG of October 1971). In such railways having a so-called outside enclosure of the support beam by the vehicles, the aforesaid described suspended guide can only be used if socalled rigid switches (without adjustable switch parts) are not at all used.

Therefore, the purpose of the invention is to illustrate a solution how one manages, in a suspended railway of the last-mentioned type in the zone of switches, without adjustable switch parts.

To attain this purpose, the invention suggests for the switch zone an arrangement of at least three support beams which are tapered on one side toward the center portion of the switch and terminate, of which support beams one (the first one) extends from the switch entrance into the center portion of the switch and is arranged there with equal lateral distance between the two other support beams extending from the switch exit into the center portion of the switch, and this arrangement involving equal lateral distance is such that the straight surface of the first one extends parallel to an oppositely positioned inclined surface of the (second) one of these two (other) support beams, which one is curved corresponding to the switch radius and that the second surface of the first one which contributes to its tapering and is curved corresponding to the switch radius extends parallel to an oppositely positioned surface which is curved to the same degree and contributes to the tapering of the third support beam. The center portion of the switch refers hereby approximately to the Zone in which the first support beam is arranged between the two other ones.

In such an arrangement, the first support beam is part of the support construction of both the through-going and also the off-branching paths of travel, whereby the sloped surface of the second support beam is associated with the through-going path of travel, the curved surface of the third support beam with the off-branching path of travel. To maintain the gauge of the path of travel, which is predetermined by the width of the support beams at the switch entrance or exit, it is thereby only necessary that both the distance between the second (straight) surface of the third support beam, which surface extends into the center portion of the switch, and the straight surface of the first support beam and also the distance between the curved surface of the first support beam and the second (curved) surface of the second support beam, which surface extends into the center portion of the switch, corresponds to the width of the support beams (at the switch entrance or switch exit).

The suggested arrangement permits, in beam tracks having an outside enclosure of the support beams by vehicles, the use of a magnetic suspended guide for the vehicles, at least in the same advantageous manner as in known beam tracks, having an inside enclosure of the vehicles. Adjustable parts'are not required for a support and guidance and also for steering into desired directions of travel. Further, adjustable parts are also not required for the switches or for the vehicles. It is only necessary to use, in a suitable manner, the common components of the magnetic suspension technique, such as electromagnets which function as support and guide magnets and magnetically conductive support and guide rails.

This will be explained more in detail hereinafter by one exemplary embodiment of the invention and further developments of the same in connection with the drawings, in which:

FIG. 1 is a top view of three support beams and an arrangement of rows of electromagnets and of support and guide rails in the zone of a switch, whereby the electromagnets (only schematically illustrated) and the support beams and the rails are illustrated partially sectioned;

FIG. 2 is a cross-sectional view of the switch along the line IlII of FIG. 1 and the back view of a vehicle which is positioned at this point; and

FIGS. 3 to 7 are further cross-sectional views of the switch along the lines llllll, [VIV, VV, VIVI and also VII-VII of FIG. 1, whereby at these positions only the important parts of the vehicle according to FIG. 2 are illustrated.

It is here remarked that the switch arrangement illustrated in FIG. 1 is considerably shorter than is the case in reality because of illustrative reasons. FIGS. 2 to 7 refer to this arrangement having approximately three times the length which corresponds to the length of a slow running switch.

A switch (FIG. 1) of a so-called one-beam railway capable of magnetically suspending and guiding vehicles 1 consists of three support beams 2, 3 and 4 which are tapered on one side toward the central position 5 at which position they terminate. The (first) support beam 2, which extends from the switch entrance into the central position 5 of the switch is arranged between the two other support beams 3 and 4. The support beams 3 and 4 extend from the switch exit into the central position 5 of the switch and are spaced the same lateral distance from said support beam 2 but on opposite sides thereof. The straight surface 6 on one side of the first support beam 2 extends parallel to an oppositely positioned sloped surface 7 of the (second) support beam 3 which is curved corresponding to the switch radius. The second surface 8 on the opposite side of the first support beam 2 is curved corresponding to the switch radius and extends parallel to an oppositely positioned surface 9 on the third support beam 4, which surface 9 is curved to the same degree as the surface 8. Furthermore, the arrangement of the support beams 2, 3 and 4 is chosen in such a manner that the distance between the second (straight) surface 10 on the third support beam 4, which surface 10 extends into the central portion 5 of the switch, and the straight surface 6 on the first support beam equals the distance between the curved surface 8 on the first support beam 2 and the second (curved) surface 11 on the second support beam 3, which surface 1 1 extends into the central portion 5 of the switch. These distances correspond to the width of each support beam at the switch entrance and also switch exit.

As can further be taken from FIG. 1, with the exception of the sloped surface 7 of the second support beam 3 and the curved surface 9 of the third support beam 4, magnetically conducting support rails 14 are arranged along all aforementioned surfaces 6, 8, 10 and 11 and along the second curved surface 12 of the second support beam 3 and the second straight surface 13 of the third support beam 4. Said support rails 14 serve as an armature for electromagnets 15, which are arranged in horizontal position on driving legs 16 of the respective vehicle 1 as support magnets (FIGS. 2 to 7).

Furthermore, magnetically conductive guide rails 17 are provided along the curved surfaces 11 and 12 of the second support beam 3 and along the straight surfaces 10 and 13 of the third support beam 4 as an armature for electromagnets 18 (guide magnets) which are arranged in vertical position on the driving legs 16 of the vehicle 1. Such guide rails 17 are, according to FIG. 2, also provided on the surfaces of the first support beam 2, however, only up to the switch entrance (compare FIG. 1). In the zone of the tapered portion of said support beam 2, one row each of electromagnets serving as stationary guide magnets l9'extends along both its surfaces 6 and 8, whereby these electromagnets are arranged in vertical position; they have the same polarity as the aforementioned guide magnets 18 of the vehicle 1. Finally, further rows of electromagnets are provided on two outer supports 20 and 21 which extend approximately through the entire switch zone. That is, for each support, one row of electromagnets are horizontally arranged and function as stationary support magnets 22 for the magnetically conductive support rails 23 of the vehicle I. The row extends approximately through the zone of the tapered portion of the first support beam 2, and, arranged above this row, a row of electromagnets are vertically arranged and function as further stationary guide magnets 24 for the magnetically conductive which does not face its support and guide magnets 15 or 18.

Of the two supports 20 and 21, one extends curved relative to the switch radius and has a lateral distance parallel to the curved surface 11 of the second support beam 3; the other, straight support 21 extends with the same lateral distance parallel to the straight surface 10 of the third support beam 4.

According to FIGS. 4 to 6, the support rails 23 of the vehicle I serve, depending on the desired driving direction, also as an armature for a row of electromagnets 26 which extend along the sloped surface 7 on the second support beam 3 or a row of electromagnets 26 which extend along the curved surface 9 on the third support beam 4 which electromagnets are horizontally arranged and function as further stationary support magnets. The arrangement of these rows and the stationary support rails 14 is chosen in such a manner that at the end of the rows their electromagnets 26 are able to cooperate with the then oppositely positioned support rail 23 of one driving leg 16 and simulataneously the support magnets 15 of the driving leg with the then oppositely positioned stationary support rail 14 (compare FIG. 6).

A driving through of the aforedescribed switch by straight-ahead travel will be discussed in connection with FIGS. 2 to 7; the position chosen therein for the vehicle 1 is valid thus for a travel without any change in direction.

Outside of the switch, thus on the open track, the vehicle l is maintained in its suspended position with respect to the stationary support rails 14 by its support magnets 15 and is guided by its guide magnets 18 with respect to the stationary guide rails 17 in lateral direction (FIG. 2). The magnetic pulls between the guide magnets 18 and guide rails 17 can be determined thereby in the usual manner by controlling the excitation of the guide magnets so that the vehicle 1 is held constantly in a central position between the two guide rails.

Upon entrance of the vehicle 1 into the switch, the support magnets 17 of the left driving leg 16 automatically slowly lose their effectiveness due to the tapering of the first support beam 2 with respect to the associated support rail 14. For this reason, the vehicle 1 is held suspended starting wtih the switch entrance on its left side, also by means of the support rail 23 (of the respective driving leg 16) by the support magnets 22 of the straight support 21, which support magnets are positioned opposite the support rail 23 (FIG. 3). Advanta geously during the transition onto these controllable support magnets 22, their excitation will be increased for a short period of time. Since this transition (from supporting by means of the suport magnets 15 of the vehicle to supporting by means of the stationary support magnets 22) takes place slidingly, the stationary support magnets 22 will furthermore be dimensioned smaller toward the switch entrance. With this, it is assured for driving through the switch in an opposite direction (from the switch exit toward the switch entrance) that the support magnets 15 of the vehicle take over automatically a support function at the switch entrance.

What concerns the guiding of the vehicle 1 during an entrance into the switch, the guide magnet or guide magnets 18 of the left driving leg 16 are turned off; the controllable guide magnets 24 of the support 21 take over in connection with the guide rail 25 of the driving leg the guiding function. Simultaneously therewith on the right vehicle side the guide magnet 18 or the guide magnets 18 of the right driving leg 16 and the guide magnets 19 on the straight surface 6 of the first support beam 2 exert repulsive forces onto one another. These stationary guide magnets 19 and those of the right vehicle leg 16 are energized steadily while the excitation of the aforementioned stationary guide magnets 24 is controlled. In this manner, a unique guide of the vehicle 1 is achieved, that is, through the teamwork of the attractive and repulsive magnetic forces a required nominal distance can be maintained between the left guide rail 25 of the vehicle and the stationary guide magnets 24 and therewith the desired direction of travel (straight ahead) can be determined exactly.

In the central portion 5 of the switch (FIG. 4), the support rail 14 for the support magnets 15 of the right driving leg 16 terminate. Its function is taken over by the electromagnets 26 on the sloped surface 7 of the second support beam 3 in connection with the support rail 23 of the right driving leg 16, whereby a continuous transition to a support by means of the support beam 3 through a not illustrated one-sided tapering of the stationary support rail 14 toward its end is achieved. On the left vehicle side, the support magnets 15 of the left driving leg in connection with the support rail 14 of the straight surface 10 of the third support beam 4 take over the supporting function again. A continuous transition is here also achieved by the (not illustrated) slow widening of the left support rail 14 and, if necessary, by a reduction of the excitation of the stationary support magnets 22 (of the straight support 21).

The guide magnets 24 of the straight support 21 and the guide magnets 18 of the left driving leg 16 guide the vehicle 1 in the center portion 5 of the switch at the end of the row of the guide magnets 19 of the straight surface of the first support beam 2 (FIG. 5). Through the cooperation of said guide magnets 18 and 24 with respect to the left driving leg an exact guidance of same is obtained and therewith of the vehicle along the third support beam 4. At the end of the guide magnets 24 of the support 21 (switch exit) the guide finally is accomplished along the third support beam 4 by the guide magnets 18 on both driving legs 16 (FIG. 7). According to FIG. 6, prior to this on the right vehicle side, a transition takes place from a support by means of the electromagnets 26 of the second supportbeam 3 to a support by means of the support magnets 15 on the right driving leg in connection with the support rail 14 (also tapered on one side toward the end) on the second straight surface 13 of the third support beam 4. At the chosen arrangement of this support rail 14 with respect to the electromagnets 26 (in two planes), it is possible to carry out the transition continuously.

It is remarked that also during the guiding function, a continuous transition from one system to the other one can be achieved by stationary guide rails 17 which continuously widen (in the respective zones) in driving direction and by continuously decreasing magnetic forces in the stationary guide magnets 19 and 24. The described magnetic lateral guiding has the advantage that also in case of a power loss in the vehicle 1 or in the switch, the vehicle is guided still in the predetermined direction. In the first case, only the stationary guide magnets effect the direction guidance; in the last case, only the steadily energized guide magnets of the vehicle effect the guidance.

The support and guidance of the vehicle during a change of the direction of travel (traveling of curves) is done in the same manner; the respective stationary support and guide magnets 22 or 24 of the curved support 20, the guide magnets 19 on the curved surface 8 of the first support beam 2 and the electromagnets 26 on the curved surface 9 of the third support beam 4 are then active.

The vehicle can be driven by a linear motor, whereby advantageously a linear motor having translators arranged in duplicate on both sides of the vehicle and having stators secured on the surfaces of the support beams 2, 3 and 4. The translators may be secured above the guide magnets on the respective driving leg in horizontal position. The stators may extend along the surfaces (6, 8, 10, 11, 12, 13) of the support beams, which surfaces are provided with support rails; in as far as stationary guide rails are present, the stators can form one structural unitwith the guide rails. In the switch therefore, at least one vehicle side, the vehicle is driven at a constant level.

The energy suply to the vehicle can come from contact rails which are arranged also along the surfaces of the support beams, which surfaces are provided with support rails, that is, below the support rais. In the central portion 5 of the switch, it is then only necessary to switch over, for example, during a drive through the switch, without changing the direction of travel, from the contact rails on the straight surface of the first support beam 2 to those on the straight surface of the third support beam 4, which latter straight surface extends into the central portion 5 of the switch.

Finally, the driving legs 16 of the vehicle can be provided with emergency-running elements which, for example, during a breakdown of the energy supply in the switch and/or in the vehicle are guided on emergencyrunning surfaces which are provided below the driving legs between the support beams and there effect, if needed, an emergency stopping of the vehicle. Emergency-running surfaces can be provided also on all surfaces of the support beams for the emergency-running elements to engage when in a vertically aligned position.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a switching zone for a magnetic suspended railway having means defining a switch entrance and a pair of switch exits and means defining a support beam at said switch entrance and said switch exits on which at least one vehicle having a pair of laterally spaced means defining driving legs thereon is supported in a suspended position by means defining conductive rails and guided by first guide magnets positioned relative to said conductive rail means, said first guide magnets being mounted on opposed surfaces of said driving legs, said conductive rail means being mounted on oppositely facing surfaces of said support beam means outside of said switching zone, said support beam means being partly enclosed by said driving legs on said vehicle, the improvement comprising wherein, within said switching zone, said support beam means comprises at least three support beams which are each tapered on one side toward a central portion of said switching zone and terminate at said central portion, a first support beam including support means extending from said switch entrance into said central portion and between the remaining two of said support beams, said remaining two of said support beams extending from said central portion to one of said switch exits, the spacing between said first support beam and said remaining two support beams in said central portion being equal, means in said central portion of said switching zone defining a pair of second guide magnets, one on each side of said first support beam, for establishing a magnetic coupling with said first guide magnets in said central portion and on at least one side of said vehicle, said first and second guide magnets having identical polarity, means defining first magnetically conductive guide rails on the opposite side of said driving legs from said second guide magnets and means defining a pair of third guide magnets for establishing a magnetic coupling with said first conductive guide 'rail means in said central portion and on at least the other side of said vehicle from said one side.

2. The improvement according to claim 1, wherein said conductive rail means is composed of magnetically conductive support rails and second magnetically conductive guide rails, said vehicle being supported in a suspended position by a magnetic coupling between means defining said conductive support rails and first support magnets and guided by said first guide magnets positioned relative to said second magnetically conductive guide rails.

3. The improvement according to claim 2, wherein said conductive support rails are mounted on opposite sides of said first support beam including said support means and extend into said central portion of said switching zone and terminate at said central portion,

said conductive support rails being also mounted on one side of said remaining two of said support beams remote from said support means and extend into said central portion of said switching zone and terminate at said cental portion.

4. The improvement according to claim 3, wherein said second magnetically conductive guide rails are mounted on said one side of said remaining two of said support beams and extend into said central portion of said switching zone and terminate at said central portion.

5. The improvement according to claim 2, wherein said second guide magnets are mounted on opposite sides of said first support beam and opposing said first guide magnets on said driving legs, said second guide magnets extending from an external portion of said central portion of said switching zone into said central portion and terminating thereat, said second magnetically conductive guide rail means are mounted on oppositely facing surfaces of said first support beam and terminate at the location where said second guide magnets begin and extend into said central portion.

6. The improvement according to claim 2, wherein said conductive rail means further comprises second magnetically conductive support rails and second support magnets, said vehicle being supported in a suspended position by a magnetic coupling between said second conductive support rails and said second support magnets, said magnetic coupling between one of said first mentioned support rails and said first support magnets supporting one side of said vehicle whenever said magnetic coupling exists between said second support rails and said second support magnets.

7. The improvement according to claim 6, wherein said second support magnets and said third guide magnets are mounted on supports which extend along and oppose the outwardly facing surfaces of said first support beam andsaid remaining two support beams in said central portion of said switching zone and said first support rails and said first guide rails mounted thereon, one of said supports being curved to accommodate a change of direction between said first support beam and one of said remaining support beams.

8. The improvement according to claim 7, wherein the other of said supports is straight.

9. The improvement according to claim 7, wherein said conductive rail means further comprises third support magnets mounted on the sides of said remaining two support beams opposing each other and said first support beam and are adapted to magnetically cooperate with said second support rails on said driving legs of said vehicle.

10. The improvement according to claim 9, wherein said third support magnets are in a different horizontal plane than said first mentioned conductive support rails.

11. The improvement according to claim 1, wherein said second guide magnets are mounted on opposite sides of said first support beam and opposing said first guide magnets on said driving legs, said second guide magnets extending from an external portion of said central portion of said switching zone into said central portion and terminating thereat. 

1. In a switching zone for a magnetic suspended railway having means defining a switch entrance and a pair of switch exits and means defining a support beam at said switch entrance and said switch exits on which at least one vehicle having a pair of laterally spaced means defining driving legs thereon is supported in a suspended position by means defining conductive rails and guided by first guide magnets positioned relative to said conductive rail means, said first guide magnets being mounted on opposed surfaces of said driving legs, said conductive rail means being mounted on oppositely facing surfaces of said support beam means outside of said switching zone, said support beam means being partly enclosed by said driving legs on said vehicle, the improvement comprising wherein, within said switching zone, said support beam means comprises at least three support beams which are each tapered on one side toward a central portion of said switching zone and terminate at said central portion, a first support beam including support means extending from said switch entrance into said central portion and between the remaining two of said support beams, said remaining two of said support beams extending from said central portion to one of said switch exits, the spacing between said first support beam and said remaining two support beams in said central portion being equal, means in said central portion of said switching zone defining a pair of second guide magnets, one on each side of said first support beam, for establishing a magnetic coupling with said first guide magnets in said central portion and on at least one side of said vehicle, said first and second guide magnets having identical polarity, means defining first magnetically conductive guide rails on the opposite side of said driving legs from said second guide magnets and means defining a pair of third guide magnets for establishing a magnetic coupling with said first conductive guide rail means in said central portion and on at least the other side of said vehicle from said one side.
 2. The improvement according to claim 1, wherein said conductive rail means is composed of magnetically conductive support rails and second magnetically conductive guide rails, said vehicle being supported in a suspended position by a magnetic coupling between means defining said conductive support rails and first support magnets and guided by said first guide magnets positioned relative to said second magnetically conductive guide rails.
 3. The improvement according to claim 2, wherein said conductive support rails are mounted on opposite sides of said first support beam including said support means and extend into said central portion of said switching zone and terminate at said central portion, said conductive support rails being also mounted on one side of said remaining two of said support beams remote from said support means and extend into said central portion of said switching zone and terminate at said cental portion.
 4. The improvement according to claim 3, wherein said second magnetically conductive guide rails are mounted on said one side of said remaining two of said support beams and extend into said central portion of said switching zone and terminate at said central portion.
 5. The improvement according to claim 2, wherein said second guide magnets are mounted on opposite sides of said first support beam and opposing said first guide magnets on said driving legs, said second guide magnets extending from an external portion of said central portion of said switching zone into said central portion and terminating thereat, said second magnetically conductive guide rail means are mounted on oppositely facing surfaces of said first support beam and terminate at the location where said second guide magnets begin and extend into said central portion.
 6. The improvement according to claim 2, wherein said conductive rail means further comprises second magnetically conductive support rails and second support magnets, said vehicle being supported in a suspended position by a magnetic coupling between said second conductive support rails and said second support magnets, said magnetic coupling between one of said first mentioned support rails and said first support magnets supporting one side of said vehicle whenever said magnetic coupling exists between said second support rails and said second support magnets.
 7. The improvement according to claim 6, wherein said second support magnets and said third guide magnets are mounted on supports which extend along and oppose the outwardly facing surfaces of said first support beam and said remaining two support beams in said central portion of said switching zone and said first support rails and said first guide rails mounted thereon, one of said supports being curved to accommodate a change of direction between said first support beam and one of said remaining support beams.
 8. The improvement according to claim 7, wherein the other of said supports is straight.
 9. The improvement according to claim 7, wherein said conductive rail means further comprises third support magnets mounted on the sides of said remaining two support beams opposing each other and said first support beam and are adapted to magnetically cooperate with said second support rails on said driving legs of said vehicle.
 10. The improvement according to claim 9, wherein said third support magnets are in a different horizontal plane than said first mentioned conductive support rails.
 11. The improvement according to claim 1, wherein said second guide magnets are mounted on opposite sides of said first support beam and opposing said first guide magnets on said driving legs, said second guide magnets extending from an external portion of said central portion of said switching zone into said central portion and terminating thereat. 